feat(capability-requests): add cross-domain capability catalog and request routing

Introduces a capability catalog (CUST-WP-0022) so domains can advertise what
they provide and agents can request capabilities from other domains with
auto-routing, lifecycle tracking, and task-unblocking on completion.

- New models: CapabilityCatalog, CapabilityRequest with full lifecycle
  (requested → accepted → in_progress → ready_for_review → completed/rejected/withdrawn)
- Migration i6d7e8f9a0b1: capability_catalog + capability_requests tables
- Router /capability-catalog and /capability-requests with accept/status endpoints
- 7 new MCP tools: register_capability, list_capabilities, request_capability,
  accept_capability_request, update_capability_request_status,
  list_capability_requests, get_capability_request
- StateSummary gains open_capability_requests count
- Dashboard: capability-requests.md page + docs/capabilities.md + docs/scope.md
- SCOPE.md: three seed capabilities documented (MCP registration, state tracking, SBOM)
- scope.template: Provided Capabilities section with example block
- scripts/ingest_capabilities.py + make ingest-capabilities[/-all] targets

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

api/schemas/capability_request.py

@@ -0,0 +1,79 @@
+import uuid
+from datetime import datetime
+
+from pydantic import BaseModel, ConfigDict
+
+
+# ---------------------------------------------------------------------------
+# Capability Catalog schemas
+# ---------------------------------------------------------------------------
+
+class CatalogCreate(BaseModel):
+    domain: str  # slug, resolved to domain_id in router
+    capability_type: str
+    title: str
+    description: str | None = None
+    keywords: list[str] = []
+
+
+class CatalogRead(BaseModel):
+    model_config = ConfigDict(from_attributes=True)
+
+    id: uuid.UUID
+    domain_slug: str
+    capability_type: str
+    title: str
+    description: str | None = None
+    keywords: list[str] = []
+    status: str
+    created_at: datetime
+    updated_at: datetime
+
+
+# ---------------------------------------------------------------------------
+# Capability Request schemas
+# ---------------------------------------------------------------------------
+
+class CapabilityRequestCreate(BaseModel):
+    title: str
+    description: str | None = None
+    capability_type: str
+    priority: str = "medium"
+    requesting_domain: str  # slug, resolved to domain_id in router
+    requesting_agent: str
+    requesting_workstream_id: uuid.UUID | None = None
+    blocking_task_id: uuid.UUID | None = None
+
+
+class CapabilityRequestAccept(BaseModel):
+    fulfilling_agent: str
+    fulfilling_workstream_id: uuid.UUID | None = None
+
+
+class CapabilityRequestStatusPatch(BaseModel):
+    status: str  # in_progress | ready_for_review | completed | rejected | withdrawn
+    note: str | None = None
+
+
+class CapabilityRequestRead(BaseModel):
+    model_config = ConfigDict(from_attributes=True)
+
+    id: uuid.UUID
+    title: str
+    description: str | None = None
+    capability_type: str
+    priority: str
+    status: str
+    requesting_domain_slug: str
+    requesting_agent: str
+    requesting_workstream_id: uuid.UUID | None = None
+    fulfilling_domain_slug: str | None = None
+    fulfilling_agent: str | None = None
+    fulfilling_workstream_id: uuid.UUID | None = None
+    blocking_task_id: uuid.UUID | None = None
+    catalog_entry_id: uuid.UUID | None = None
+    resolution_note: str | None = None
+    accepted_at: datetime | None = None
+    completed_at: datetime | None = None
+    created_at: datetime
+    updated_at: datetime